Most cancer deaths are attributable to the metastatic phase of the disease. However, the molecular and cellular mechanisms that allow tumor cells to leave the primary site, survive during transit through the blood and establish and maintain a new tumor in a secondary organ remain poorly understood. Using a genetically engineered mouse model of metastatic non-small cell lung cancer in which primary tumors can be unambiguously linked to their metastases, we will systematically and comprehensively characterize alterations at the genetic, gene expression, and epigenetic levels. The model utilizes conditional mutations in the K-Ras oncogene and the p53 tumor suppressor gene, which are both mutated at high frequency in human lung cancer. These studies will employ cutting-edge methods in molecular genetic analysis, relying extensively on next generation DNA sequencing technology. In addition, we will use transposon-mediated mutagenesis system to perform a forward genetic screen to identify genes that enhance metastatic behavior. Data from these studies will be subjected to integrative bioinformatic analysis to increase the ability to identify metastasis pathways, including performing cross-species analysis with data from human lung cancer specimens. Candidate genes and pathways will be validated in large series of tumors and metastases from the mouse model as well as in human lung cancer patient samples. We will probe the biological function of candidate metastasis genes and pathways using a combination of cell-based and in vivo approaches, including altering gene function in the autochthonous model. The information gained from these studies is expected to provide new insights into the biological basis of metastasis in mouse models and in human lung cancer. An improved understanding of these processes has the potential to improve diagnosis of aggressive lung cancer, lead to treatments that target metastatic lesions as well as methods to inhibit metastatic spread. Given that an estimated 1.4 million individuals will succumb to lung cancer in the United States and throughout the world over the next year, most of them from the consequences of metastasis, new insights into lung cancer metastasis are highly relevant to human health.